Silicon particles having a particle diameter of nanometer order have physical and chemical properties, which are considerably different from bulk silicon such as monocrystalline silicon, and are expected to be applied to novel functional materials.
Among the ultrafine particles of a semiconductor, metal and the like, those having a particle diameter smaller than a wavelength (about 10 nm) of electrons, or a nanometer order or less, are known that they have peculiar physical properties different from those of a bulk body because an effect of the finite nature of the size to the movements of electrons becomes large.
For silicon taking the most significant position among various types of semiconductor materials, its particles having a particle diameter, which is miniaturized to a nanosize, are reported that they emit light with a wavelength different from a silicon monocrystalline bulk body, indicating that a band structure and a surface level effect are different from the bulk body (see Nonpatent Literature 1).
Crystalline silicon particles having a particle diameter of a nanometer order or less are in an aggregate form comprising several to several hundred numbers of silicon atoms, and have a particle diameter of several angstroms to several nanometers depending on the number of silicon atoms, which is about 6 angstroms (0.6 nm) in case of, for example, Si10.
In terms of the structure, there are also crystalline silicon particles not having a diamond structure other than the crystalline silicon particles having the diamond structure similar to the bulk body silicon monocrystal.
Thus, the crystalline silicon particles can have various sizes and atomic positions and develop different physical properties respectively. Therefore, if the crystalline silicon particles whose size and atomic arrangement are appropriately controlled can be produced, there is a possibility that they can be applied to novel functional materials.
Conventionally, as a method for producing crystalline silicon particles having a particle diameter of a nanometer order or less, there are a method of irradiating an ultraviolet laser beam to a gaseous silicon compound (see Patent Literature 1), a method of performing laser ablation of a silicon target (see Patent Literature 2), a method of growing a crystal after the production of a nucleus of fine Si monocrystalline particles from SiH2 radical in argon plasma (see Patent Literature 3), a method of irradiating a laser beam to a amorphous silicon film (see Patent Literature 4), and the like.
The crystalline silicon particles obtained by the methods of Patent Literatures 1 and 2 are monosilicon particles. The silicon particles obtained by the method of Patent Literature 3 are monosilicon particles and, if necessary, have the surfaces coated with an oxide film, a nitride film or the like. Such crystalline silicon particles have a problem that their arrangement is difficult because they are fine particles of a nanometer order when a semiconductor element is formed by arranging them in a particular pattern on a substrate.
The crystalline silicon particles obtained by the method of Patent Literature 4 are present in an amorphous silicon film, so that it is also possible to form by arranging the particles in a pattern form by a laser beam irradiation method. But, the matrix is not an insulator but semiconductor amorphous silicon similar to the crystalline silicon particles, and the arranged particles and the matrix have similar electrical characteristics, so that it is hard to make them function without modification as a semiconductor element.
[Patent Literature 1]
    Japanese Patent Laid-Open Publication No. HEI 06-072705.[Patent Literature 2]    Japanese Patent Laid-Open Publication No. 2001-257368.[Patent Literature 3]    Japanese Patent Laid-Open Publication No. 2002-076358.[Patent Literature 4]    Japanese Patent Laid-Open Publication No. 2002-176180.[Nonpatent Literature 1]    Nikkei Advanced Technology Report, issued on Jan. 27, 2003, pp 1 to 4